<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>    
    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>

</head>
<body>
    <div id="app">
        <p>{{msg}}</p>
        <my-component @change-msg="changeMsg"></my-component>
    </div>
    <script>
        Vue.component("my-component",{
            template:`
                <div>
                    <button @click="$emit('change-msg')">点击</button>
                </div>
            `
        });




      new Vue({
          el:"#app",
          data:{
              msg:"你好"
          },
          methods: {
              changeMsg(){
                  this.msg="哈哈哈"
              }
          },
      });
    
    </script>
</body>
</html>